The present invention relates generally to catheters, and more particularly to long-term catheter systems, such as long-term dialysis catheter systems, and associated methods of maintaining blood flow in catheter systems.
Various medical procedures require that a patient be catheterized. For example, catheterization may be required when a patient undergoes hemodialysis or has a clot aspirated from a blood vessel. Generally, the length of time the patient will be catheterized dictates whether a physician will utilize a "temporary catheterization technique" (i.e. a technique in which the catheter is left in a blood vessel for a relatively short period of time such as a few minutes, hours, days, or weeks) or a "permanent catheterization technique" (i.e. a technique in which the catheter is left in a blood vessel for a relatively long period of time such as several months or indefinitely).
For example, a procedure in which a clot is aspirated from a blood vessel typically includes placing the catheter in the blood vessel for a relatively short period of time such as a few minutes to a few hours and then withdrawing the catheter once the clot has been removed. Therefore, when performing such an aspiration procedure, it is common for a physician to use the temporary catheterization technique to place the catheter in the blood vessel of the patient.
On the other hand, when a procedure is performed to effect hemodialysis, a physician may place a catheter in the blood vessel for a relatively long period of time. In particular, a patient suffering from kidney failure who is involved in a hemodialysis regimen typically requires a dialysis session three days per week for an indefinite period of time whereby extra fluid, chemicals, and wastes are removed from his/her body. A patient who is involved in such a hemodialysis regimen may need a catheter placed in his/her blood vessel for a relatively long period of time in order to provide a ready means for vascular access into his/her bloodstream over such relatively long period of time. This long term placement of the catheter for dialysis purposes may be desirable for a number of reasons.
Firstly, a patient may have experienced progressive loss of other conventional long term vascular access possibilities such as surgically created arteriovenous fistulas. Accordingly, the long term placement of the catheter in the patient's blood vessel may be the best alternative for the patient as he/she proceeds with the hemodialysis regimen.
Additionally, the long term placement of the catheter in the patient's blood vessel may be desirable after initial creation of an arteriovenous fistula in the patient's body. In particular, it is desirable to provide a ready means for vascular access into the patient's bloodstream during a maturation period of the arteriovenous fistula. The maturation period allows the arteriovenous fistula to develop sufficiently so that it will function as a ready means for vascular access into the patient's bloodstream which may be safely punctured multiple times per week for hemodialysis. The length of time of this maturation period is typically on the order of several weeks (e.g. three weeks) to many months (e.g. six months).
Therefore, when performing a hemodialysis procedure, it is common for a physician to use the permanent catheterization technique to place the catheter in the blood vessel of the patient.
These two catheterization techniques are significantly different with respect to their complexity and degree of invasiveness. For example, in the case of the temporary catheterization technique, it is common to insert a temporary catheter into a patient's blood vessel using a "direct puncture technique." This technique entails creating a small incision in a patient's skin with a scalpel directly over the blood vessel to be catheterized. A needle is then advanced through the skin incision and subcutaneous tissue and into the blood vessel. Thereafter, a guidewire is advanced through the needle into the blood vessel and the needle is subsequerntly removed over the guidewire. Then, one or more tubular vessel dilators are used to widen the opening defined in the skin and subcutaneous tissue, and further to widen the opening defined in the blood vessel wall to a caliber similar to that of the temporary catheter. The temporary catheter is then advanced over the guidewire and into the blood vessel. Thereafter, the guidewire is removed.
When the temporary catheterization technique is used during a clot aspiration procedure, two catheters are usually placed in the blood vessel of a patient. In particular, an outer catheter is usually placed within the blood vessel using the above described direct puncture technique so that its distal opening is located near the clot. Thereafter, an inner catheter having a smaller caliber relative to the outer catheter is advanced through a lumen of the outer catheter. While the inner catheter is positioned within the outer catheter, an aspiration vacuum is applied to the inner catheter with a syringe. If the size of the clot (or fragments thereof) are smaller than the inner diameter of the inner catheter, then the clot or clot fragments are drawn into and through the inner catheter thereby removing the clot from the blood vessel. If the size of the clot or clot fragments are larger than the inner diameter of the inner catheter, then the clot or clot fragments are drawn to a location adjacent to the distal orifice of the inner catheter. Subsequently, while the aspiration vacuum is still being applied, the inner catheter is withdrawn from the outer catheter thereby additionally withdrawing the clot or clot fragments from the outer catheter and the patient's blood vessel. Thereafter, the outer catheter remains temporarily in place within the blood vessel of the patient for subsequent injections of radiographic contrast for imaging purposes to determine the extent of clot remaining in the blood vessel as well as to determine if clot has migrated to another location within the blood vessel. The outer catheter, which remains temporarily in place in the blood vessel, provides a conduit for the inner catheter to be advanced back into the patient's blood vessel for additional aspiration attempts which are usually required for complete removal of the clot from the blood vessel.
If an outer catheter needs to be replaced during a clot aspiration procedure because of catheter malfunction, such replacement can be accomplished by advancing a guidewire through the lumen of the outer catheter and into the blood vessel. The existing outer catheter can then be removed over the guidewire to a location outside of the patient's body. Thereafter, a new outer catheter is placed in the patient's blood vessel by advancing the new outer catheter over the guidewire as discussed above.
In contrast to the temporary catheterization technique, the permanent catheterization technique typically entails inserting a permanent catheter into a patient's blood vessel using a "tunneled catheter technique." The tunneled catheter technique includes (i) creating a first opening by making a small incision in a patient's skin with a scalpel directly over the blood vessel to be catheterized, (ii) puncturing the blood vessel at a location directly below the first opening by advancing a needle through the skin incision and subcutaneous tissue and into the blood vessel, (iii) advancing a guidewire through the needle into the blood vessel, (iv) removing the needle over the guidewire, (v) passing one or more tubular vessel dilators over the guidewire to widen the opening defined in the skin and subcutaneous tissue, and further to widen the opening defined in the blood vessel wall to a caliber similar to that of the tubular guide, (vi) advancing the tubular guide over the guidewire and into the blood vessel, (vii) thereafter, creating a second opening in the patient's skin spaced apart at least several centimeters from the first opening, (viii) advancing a tunneling instrument from the second opening to the first opening so as to create a passageway within the subcutaneous tissue under the skin between the first opening and the second opening, (ix) advancing a permanent catheter having a tissue ingrowth member attached to an outer surface thereof into the second opening and through the passageway such that a distal end of the permanent catheter is located adjacent the first opening, (x) inserting the distal end of the permanent catheter through the tubular guide member and into the blood vessel to be catheterized whereby the tissue ingrowth member is positioned in the subcutaneous tissue, (xi) removing the tubular guide member, and (xii) closing the first opening with suture whereby the permanent catheter (a) is no longer exposed through the first opening, (b) extends for at least several centimeters under the patient's skin between second opening and the location where the permanent catheter enters the blood vessel, and (c) extends out of the second opening so that a proximal end of the permanent catheter is located outside of the patient's body.
In contrast to the direct puncture catheter technique, the tunneled catheter technique results in the placement of a catheter in a patient's body in a manner which allows the catheter to remain safely in the patient's body for a relatively long period of time. For example, a degree of safety is achieved by separating the following two openings by at least several centimeters: (i) the skin opening through which the catheter enters the patient's body, and (ii) the blood vessel opening through which the catheter enters the patient's vascular system. This safety feature decreases the likelihood that bacteria will migrate up the length of the catheter from the skin opening and cause an infection at the blood vessel opening.
In addition, another degree of safety is achieved by providing a tissue ingrowth member which is attached to and extends around an outer surface of the catheter. As the catheter is left in the patient's body over a period of time, the tissue ingrowth member becomes affixed to the subcutaneous tissue of the patient's body thereby providing a secure attachment of the catheter to the patient's body. Providing a secure attachment between the catheter and the patient's body reduces the likelihood that the catheter will be inadvertently removed or withdrawn from the patient's body. Moreover, since the subcutaneous tissue becomes attached to the tissue ingrowth member, a physical barrier is created between following two openings: (i) the skin opening through which the catheter enters the patient's body, and (ii) the blood vessel opening through which the catheter enters the patient's vascular system. This physical barrier further decreases the likelihood that bacteria will migrate up the length of the catheter from the skin opening and cause an infection at the blood vessel opening.
While the tunneled catheter technique provides the significant advantage of allowing the catheter to remain safely in the patient's body for a relatively long period of time, significant disadvantages of the tunneled catheter technique exists. For example, when a catheter remains in a blood vessel for a long period of time, there is a tendency for blood clots including fibrin (e.g. in the form of a fibrin sheath) to attach to and build-up on the outer and inner surfaces of the portion of the catheter which is located within the blood vessel. The above described attachment and build-up tends to occlude the various distal openings defined in the catheter which enable fluid movement into and out of the catheter. For instance, attempts at withdrawing blood through the catheter may be unsuccessful due to blood clots creating a "ball-valve" effect which occlude the various distal openings of the catheter.
When occlusion of the various distal openings of the catheter occurs due to the above described blood clot attachment and build-up, a physician has several options for eliminating the occlusion thereby reestablishing access to the vascular system. One option is to remove the occluded catheter and replace it with a new catheter. However, in contrast to the ease of exchanging a catheter which was placed in the patient's body using the direct puncture technique, exchanging a catheter which was placed in the patient's body using the tunneled catheter technique is substantially more complicated and invasive. This is true since in order to remove the occluded catheter from the patient's body, the physician must surgically dissect the tissue ingrowth member which is secured to the outer surface of the catheter from the patient's subcutaneous tissue. Recall that the tissue ingrowth member becomes affixed to the subcutaneous tissue over a period of time. Thereafter, the physician would place a new catheter into the patient's body generally using the above described tunneled catheter technique. Thus, this option is undesirable since it requires additional surgery which further traumatizes the patient and increases the cost of the medical care.
Another option for eliminating the occlusion of the various distal openings of the catheter in order to reestablish access to the vascular system involves the performance of a medical procedure in which a blood clot-dissolving medication such as urokinase is infused into the catheter. However, this medication is not always successful in eliminating the occlusion of the various distal openings of the catheter. In addition, infusion of the medication into the catheter subjects the patient to potential bleeding complications due to the medication entering the vascular system and being circulated systemically. Further, this medication is expensive. Thus, this option has serious drawbacks as well.
An additional option for eliminating the occlusion of the various distal openings of the catheter in order to reestablish access to the vascular system involves the performance of a medical procedure in which an intravascular snare is introduced into the blood vessel in order to physically strip off any blood clots or fibrin sheath which has attached and built-up on the distal portion of the catheter. However, for catheters placed in veins, this medical procedure requires a venopuncture in the femoral or jugular vein which is invasive and can be uncomfortable for a patient. Furthermore, this option requires the use of (i) an intravascular snare, (ii) a physician experienced in catheter techniques, and (iii) an angiographic suite to provide fluoroscopic imaging. Use of each of items (i), (ii), and (iii) above causes this option to be relatively expensive. Consequently, this option also has significant disadvantages.
What is needed therefore is a method and apparatus for eliminating the occlusion of the various distal openings of a catheter which has been placed in a patient's body using the tunneled catheter technique which overcomes one or more of the above-mentioned drawbacks.